Actuarial assumption COLA

No definition available.

Name:	tve_ActuarialassumptionCOLA
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Age Threshold for Changes to COLA Related to 2016 Amendments to TVA Pension Plan

+ References

No definition available.

+ Details

Name:	tve_AgeThresholdforChangestoCOLAChangesforCashBalancePlan
Namespace Prefix:	tve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

COLA percentage increase (decrease)

+ References

No definition available.

+ Details

Name:	tve_COLApercentageincreasedecrease
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The change in the discount date or the rate of return on plan assets assumption that is used in disclosure of sensitivity of the net periodic pension cost and the projected benefit obligation to changes in those rates.

+ References

No definition available.

+ Details

Name:	tve_ChangeInDiscountRateOrRateOfReturnOnPlanAssetsAssumption
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cost of living adjustment percentage used for defined benefit plans.

+ References

No definition available.

+ Details

Name:	tve_DefinedBenefitPlanCostOfLivingAdjustmentAssumption
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of effect of change in rate on the net periodic benefit cost for pension benefits.

+ References

No definition available.

+ Details

Name:	tve_PensionBenefitPlanEffectOfChangeInRateOnNetPeriodicBenefitCost
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of effect of change in rate on the projected benefit obligation for pension benefits.

+ References

No definition available.

+ Details

Name:	tve_PensionBenefitPlanEffectOfChangeInRateOnProjectedBenefitObligation
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	tve_PensionBenefitRatesAxis=tve_PensionPlanDiscountRateMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	tve_PensionBenefitRatesAxis=tve_PensionBenefitExpectedRateOfReturnOnPlanAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_BenefitPlanParticipantClassAxis=tve_PreMedicareEligibleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
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Benefit Plans Sensitivity to Certain Changes in Pension Assumptions (Details)	12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Oct. 01, 2023	Oct. 01, 2016 Years	Sep. 30, 2016
Defined Benefit Plan Disclosure
Defined Benefit Plan, Cost of Living Adjustment Assumption	25.00%
Discount rate		3.70%
Age Threshold for Changes to COLA Changes for Cash Balance Plan \| Years				50
Discount rate
Defined Benefit Plan Disclosure
Change in Assumption	(0.25%)
Impact on Pension Cost	$ 16,000,000
Impact on Projected Benefit Obligation	$ 330,000,000
Rate of return on plan assets
Defined Benefit Plan Disclosure
Change in Assumption	(0.25%)
Impact on Pension Cost	$ 18,000,000
Other Post-retirement Benefits
Defined Benefit Plan Disclosure
Defined Benefit Plan, Cost of Living Adjustment Assumption	2.00%	2.00%			2.40%
Discount rate	4.40%	3.95%
Actuarial assumption COLA	$ 1.8400	$ 0.9900
Pension Benefits
Defined Benefit Plan Disclosure
Defined Benefit Plan, Cost of Living Adjustment Assumption	2.00%	2.00%			2.40%
COLA percentage increase (decrease)	600.00%
Discount rate	4.35%	3.85%
Pre-Medicare Eligible [Member] \| Other Post-retirement Benefits
Defined Benefit Plan Disclosure
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%	5.00%			5.00%
Scenario, Forecast \| Pre-Medicare Eligible [Member] \| Other Post-retirement Benefits
Defined Benefit Plan Disclosure
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate			5.00%